Comparing systemd targets to SysVinit runlevels

The old SysV runlevels defined which services would run when the operating system reached a certain state. It was a simple concept, except that there were four different sets of runlevel definitions that a Linux user would have to know. There was the generic set, which was created by the big Linux gurus at the Linux Foundation as part of the Linux Standard Base. The Red Hat definitions were almost identical to the generic ones. The Slackware and Debian developers basically came out of left field and created their own definitions that didn't look anything like the generic ones. (Of course, Slackware and Debian are the two oldest surviving Linux distros, so it's possible that they might have created their own definitions before the Linux Foundation gurus created the generic definitions.) This made things a bit confusing for new Linux users, especially for those of us who had to study for the Linux Professional Institute certification...